Portable gas fired art pottery kiln and method

ABSTRACT

A gas fired pottery kiln having a furnace chamber defined by a floor and an upwardly extending wall suspended within a substantially cylindrical steel shell. The furnace chamber is spaced from the bottom of the shell and supported upon insulation material. The furnace chamber wall is spaced from the steel shell, the space being filled by a refractory castable for securing the furnace chamber and providing compensation for expansion and contraction due to rapid heating and cooling.

1451 Aug. 14, 1973 3,055,652 9/1962 Remmey et 263/40 R 9/1934 Jacobi.............1...............

[ PORTABLE GAS FIRED ART POTTERY KILN AND METHOD [76] Inventor: Worden Robinson, 715 18th St., P dry E m John J Camby W t ,D.C. 20003 m xa meras mg on Attorney-Ronald L. Grudziecki Dec. 27, 1971 [22] Filed:

App]. No.: 212,445

{57] ABSTRACT A gas fired pottery kiln having a furnace chamber de- 432/120, 52/741, 432/247 51 11101 2711 3/02 fined by a and upwardly extendmg wan pended within a substantially cylindrical steel shell The furnace chamber is spaced from the bottom of the [58] Field of shell and supported upon insulation material. The fur- 56 R f cud nace chamber wall is spaced from the steel shell, the 1 e I space being filled by a refractory castable for securing UNITED STATES PATENTS the furnace chamber and providing compensation for expansion and contraction due to rapid heating and 7 Claims, 2 Drawing Figures 1,829,320 10/1931 White 3,148,238 9/1964 Willenbrock, Jr..

2,221,076 11/1940 Conn0lly...... 1,432,591 10/1922 Carll PORTABLE GAS FIRED ART POTTERY KILN AND METHOD BACKGROUND OF THE INVENTION This invention relates to a portable art pottery kiln and more particularly to a cylindrical gas fired kiln having improved strength characteristics.

The pottery art has in recent years gained in popularity and initiated interest in the development, by kiln manufacturers, of a portable kiln suitable for home use. Due to the relatively high cost associated with the man ufacture of kilns and their tendency to be quite cumbersome and heavy, the small consumer market has not heretofore been successfully tapped. A kiln suitable for home use should be relatively light and preferably portable so that it may be moved from a firing location to another area for storage. Additionally, the kiln should be rug'ged to withstand shipping and continued heating and cooling.

It can be appreciated that due to the brittle nature of the insulating fire brick usually employed in kiln construction, movement of the kiln during shipment and after being set in place for firing may cause cracking of the fire brick. Additionally, these brick could easily come loose during this rough handling. Thus, it was often necessary, in order to achieve the desired strength characteristics, to resort to weighty and expensive securing techniques for ensuring that the fire brick remain in their proper location and that they do not crack. As noted, expensive crating methods were also required for each location move.

In constructing a substantially cylindrical kiln, longi tudinally extending beveled fire fire brick defining the furnace walls have been employed in the kiln art. Various metal fastening clips also are used extensively to join these beveled fire brick together forming a furnace chamber having a generally circular cross section such as a United States Wichen Patent No. 3,112,921. Itcan be appreciated that the use of preformed metal clips to secure fire brick in place can be prohibitively expensive and adds additional weight to a kiln. This may make costs associated with the manufacture of a kiln for home use prohibitive. The insulating characteristics of these metal clips also are unsatisfactory. The prior art in the United States Bryon Patent No. 3,330,546 has even turned to embedding magnetic devices within the fire brick to provide suitable brick-holding forces. Any brick-holding technique which is to be successfully employed in commercial kiln manufacture should provide a strength suitable for militating against fire brick cracking and also provide compensation for expansion and contraction of the fire brick during kiln firing.

It is often desirable to control the rate of cooling of a kiln' after the proper firing temperatures have been reached. Complex sensors and control circuits would be impractical in portable kiln construction but a simple yet effective port control would be desirable. An inexpensive and efficient temperature control device has not, however, heretofore been proposed.

OBJECTS AND SUMMARY OF THE INVENTION It is a general object of the present invention to provide a novel kiln and method of manufacture therefore for firing pottery which has improved strength and heat insulation characteristics.

Another object is to provide a novel gas fired art pottery kiln which is provided with a furnace chamber within a steel casing wherein insulating material separates the furnace from the shell bottom and wherein a refractory castable fills the area between the steel shell and the furnace walls.

A further object is to provide a novel gas fired art pottery kiln wherein the heated furnace chamber coo|- ing rate may be accurately controlled through the use of cooperating selectively operable sealing members.

Yet another object of the invention is to provide novel gas fired art pottery kiln including a novel upper lid arrangement wherein the edge of the furnace chamber cooperates with an annular groove in the lid toseal the kiln during firing.

A still further object is to provide in a gas fired art pottery kiln a novel furnace chamber viewing arrangement including a plurality of inwardly diverging peep holes.

A portable gas art pottery kiln having an inner furnace chamber defined by a substantially circular floor and upwardly extending walls constructed of longitudinally extending tapered fire brick. Spaced from the walls, a substantially cylindrical outer steel shell is provided. The bottom of the steel shell is filled with soft insulation material. A refractory castable fills the space between the furnace chamber walls and the steel shell to form a strong monolithic structure. The refractory castable serves to securely hold the fire brick in place and provides compensation for expansion and contraction of the bricks. The castable also prevents heat from corroding the steel shell by sealing cracks. The soft insulationmaterial resists shock from the bottom of the kiln thereby protecting the furnace chamber. A removable lid having a centrally positioned flue is also provided. A gas burner is in communication with the furnace chamber through a kiln burner port in the wall.

A method of constructing a portable gas fired pottery kiln is provided. A substantially cylindrical steel shell having a sealed bottom is formed. Insulation material is then positioned on the bottom of this shell. A furnace chamber also substantially cylindrical, having a smaller diameter than that of the steel shell is formed therewithin and supported on the insulation material. A re fractory castable is poured into the space between the furnace chamber walls and the s'teel shell to form a monolithic structure.

THE DRAWINGS Other objects and advantages of the present invention will become apparent from the subsequent detailed description thereof with the accompanying drawings in which like numerals designate like elements and in which:

FIG. 1 is a front elevation view of the gas fired art pottery kiln partially in section;

FIG. 2 is a top elevation of the kiln of FIG. 1 partially in section.

DETAILED DESCRIPTION or THE PREFERRED EMBODIMENT to form a generally circular furnace when viewed from above (see FlG.l). The brick defines a polygon having a sufficient number of sides to approach a circular configuration. The fire bricks, for example, may be a low iron type sold under the tradename of H-W 23 LI by Harbison-Walker Refractories Co. of Pittsburgh, Pennsylvania. While a plurality of these brick are preferably stacked on one another to form the wall 17, an elongated brick extending upwardly from the floor may also be employed. The furnace chamber 13 is supported upon the floor 15. The outer periphery of the wall is in general alignment with that of the floor 15. These brick walls are free standing and are neither cemented nor mortared, being held in place by their tapered configuration.

A substantially cylindrical steel shell or container 21, surrounds the fire brick chamber 13 and has its walls spaced therefrom at 23. The steel shell, for example, is of a suitable thickness, e.g., 22 gauge and preferably is corrosion resistant. The shell can be formed of a galvanized steel or of a corrosion resistant alloy. This is preferable due to the corroding effects caused by heat generated during kiln firing. The bottom of the steel shell is fitted with a floor of insulating material which is preferably cemented insulation block and indicated at 25. This floor conforms to the cross-sectional shape of the shell and fills the bottom thereof. The furnace chamber 13 rests upon and is supported by this floor 25. The block forming the floor is preferably constructed of a soft material relative to the fire brick. This is desirable so that the floor of the kiln can absorb sufficient shock and stress to prevent cracking or loosening of the brick An insulated refractory castable 24 fills the space 23 between the fire brick l9 and the steel shell 21. This castable may, for example, be poured in two layers A and B the lower layer A being Plicast Airlite and the Upper layer B being Plicast Verilite both sold by the Pilbrio Company of Chicago, Illinois. This castable serves to secure the bricks in their proper position and provides compensation for expansion and contraction of the bricks 19 during kiln operation. The castable 24 is preferably poured within the space 23 and allowed to set. This castable adheres to both the brick and the steel shell to form a monolithic structure. During heating and cooling of the brick, expansion and contraction is absorbed by the castable which gives sufficiently to prevent cracking. During shipping, this castable also absorbs shock to militate against the loosening of the brick 19.

It is important to note that the expansion characteristics of the materials chosen for the fire brick walls, castable layer and outer steel shell are carefully considered in order to provide for proportional expansion and contraction. The steel shell expands the most per degree and the fire brick the least. The refractory castables expansion factor lies between the expansion factors of these two kiln members. The heat generated, however, has its greatest effect on the fire brick and is least felt at the outer shell 21. Thus, the temperature gradient is inversely proportional to the expansion characteristics of the materials forming the kiln walls. This has been found to desirably reduce brick cracking and prevent loosening.

Additionally, the use of a refractory castable to form a monolithic structure militates against air leaking into the kiln through cracks in the brick and adversely affecting kiln firing. Also, cooling of the furnace chamber after firing may be more evenly controlled when air leakage is substantially reduced and prevent shell corrosion.

The furnace chamber 13, therefore, is suspended within the castable side walls 24 and upon the insulation material 25.'Preferably, the steel shell is formed first and the kiln floor of insulation material is positioned on the bottom of the shell. The furnace chamber 13 is then formed within the shell and supported on the floor 25. As noted, the insulating refractory castable is then poured into the space between the shell and the chamber to form, when set, a strong monolithic structure.

The kiln side wall at 27 includes a burner port 29 which is tapered toward the inside of the furnace chamber 13. This burner port provides a communication path for the flammable gases which are projected therethrough to the furnace area during kiln firing. A substantially planar asbestos cover 31 is pivotally hinged to the shell 21 at 33 by a screw or other suitable fastening device. This port cover 21 has an area slightly larger than that of the burner port at its intersection with the steel shell 21 and may be pivoted to sealingly enclose the port (phantom showing FIG.2).

Also preferably secured to the kiln wall is a conventional gas burner device 35 which has a burner nozzle 37 spaced from, directed toward and in alignment with the burner port 29. This burner may be any of a number of conventional commercially available types such as a Buzzer VNB l25 sold by Charles A. Honer, Inc. of New York, N.Y. A suitable safety control is preferably included to stop gas flow when the flame has been extinguished. Additionally, a pilot control is desirable. This introduction of heat communicated through the side wall 17 of the furnace militates against the possibility of producing a hot bottom. Additionally, it advantageously causes the flame to be readily visible from the side of the kiln.

The uppermost edge of the furnace wall 17 at 39 projects above the steel shell and includes beveled corners 41 at the inner and outer peripheries of the furnace chamber 13. A kiln lid 43 also constructed of tire brick includes a recessed annular groove 45 which suitably receives the upper edge of the beveled fire brick at 39. This lid facilitates the insertion and removal of articles to be fired and seals the furnace chamber 13 at the upper edge 39.

The fire brick which form the lid 43 are preferably held together by refractory cement and by means of a circular clamping collar or ring 47 which may be tightened to clamp the bricks in a conventional manner by means of screw devices 49. Even though the fire bricks 47 are generally secured to one another by means of the refractory cement, they may loosen during continued use and may require additional securing pressure applied through the ring 47 by the screw devices 49.

Positioned centrally in the kiln lid at 51 is a flue or vent 53. This flue tapers outwardly or diverges from the inner furnace chamber and provides an escape path for gaseous combustion products from furnace chamber 13. A tapered plug 55 has a tapered shape which conforms generally to the flue opening 53 and may be selectively placed therein to prevent the escape of heat from the furnace chamber 13, thereby controlling the rate of cooling to be subsequently described. This plug 55 may also be constructed of tire brick and may include a handle 56.

The kiln is preferably provided with a pair of handles 57 which are suitably bolted or otherwise fastened to the outer shell 21 of the kiln 11. The positioning of these handles and their number is generally determined by the size and weight of the kiln. It is significant, however, to note that the aforedescribed kiln construction aids considerably in reducing the overall weight of the kiln.

Also in communication with the inner furnace chamber are a series of peep holes or viewing ports 59 which are equally vertically spaced along the walls of the kiln so that pyrometric cones may be viewed within the furnace to determine the furnace temperature. These peep holes have a generally small outer viewing area at 61 and diverge toward the furnace chamber at 63. This construction is especially advantageous in minimizing the loss of heat from the furnace chamber and in militating against the possibility of danger to the eyes when viewing the cone 71 or the pottery 65 being fired.

OPERATION In operation, the burner 35 is turned on and automatically lit by a pilot flame. The lid 43 rests on the upper edge of brick 19 at 39 and suitably seals the furnace chamber 13. The vent port 53 is open to permit the venting of combustion products from the gas burner 35. The pottery indicated at 65 may be positioned on a shelf such as 67 or on the furnace floor. These shelves may be constructed of clay or other suitable material. A shelf 68 located about one inch below the flue opening has been found to be desirable in spreading out the heat and providing an even temperature throughout the furnace chamber.

A baffle brick 69 is preferably positioned in front of the burner port 29 to deflect the flames from the burner and aid in distributing the heat therefrom. The pyrometric cone 71 may be positioned on a shelf 67 to be viewed through the side walls of the kiln by means of the peep holes 59. As known to the skilled artisan, these cones begin to deform when the desired temperature has been reached after which the burner 35 may be shut off. A kiln constructed in accordance with the invention has been successfully tired to cone l0,i.e 238lF.

For slow and controlled cooling after'shutting off burner 35, the asbestos port cover 31 may be pivoted upwardly to seal the burner port and the plug 55 may be inserted into the flue or vent 53. It can be appreciated that with insulative materials completely sur rounding the furnace chamber 13, the cooling process will be carried out at a very slow rate. The monolithic structure, as previously noted, also prevents air from leaking into the chamber 13, thereby further contributing to slow and controlled cooling. After ten hours of heating, and then fitting the port cover 31 and plug 55 into sealing position, the kiln has been found to cool over a-period of approximately hours.

The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiment is, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and intended to be covered by Letters Patent is:

l. A manually portable gas fired art pottery kiln comprising: an inner surface chamber defined by a furnace floor and upwardly extending wall means,

said chamber being constructed of at least one layer of horizontally adjacent insulating firebricks, an outer steel shell having an enclosed bottom and spaced from the outer surfaces of said firebricks, said shell including means defining a plurality of manual gripping handle means for manually lifting and transporting said kiln, a kiln floor of insulation material substantially filling the bottom of the steel shell for supporting said fur nace chamber. a burner port forming an opening from said furnace chamber and extending through said steel shell, gas burner means secured to the outer periphery of said kiln shell and in communication with said furnace chamber through said burner port for heating said furnace chamber, 7 manuallyremovable lid means, including handle means, for affording insertion and removal of objects to be fired and and having a flue positioned centrally therein, refractory castable means filling the space between said outer steel shell and all of said fire bricks and extending to said kiln floor; said refractory castable means adhering to the outer surfaces of said fire bricks and said steel shell for securing said fire bricks in place, said bricks being freestanding relative to one another and being bonded solely at their outer surfaces said bonding being accomplished by said refractory castable means.

said bricks, said refractory castable means, and said steel shell having respective heat expansion characteristics substantially inversely proportional to expected temperature gradient conditions such that said bricks, said refractory castable means, and said steel shell expand and con tractin a substantially uniform manner.

2. The kiln according to claim 1 wherein said gas burner means includes a nozzle directed toward and spaced outwardly from said burner port; insulating port cover means being pivotally secured to said steel shell for selective rotation into sealing engagement over the burner port; and a vent sealing plug, including manual gripping handle means, selectively positionable within said flue opening; said cover means and said plug cooperating to control the rate of the cooling of the tired chamber.

3. The kiln according to claim 2 wherein said burner port, said gas burner means, and said port cover are disposed at the side of said kiln.

4. The kiln according to claim 1 wherein said refractory castable means comprises an upper layer and a lower layer of refractory castable sub-, stances having different thermal expansion characteristics.

5. The kiln according to claim 1 wherein said cylindrical kiln wall means is provided with a plurality of peep holes vertically spaced from one another, each of said peep holes having a relatively small viewing opening diverging toward the interior of the furnace chamber.

6. A manually portable gas fired art pottery kiln comprising:

a cylindrical inner surface chamber defined by a furnace floor and upwardly extending cylindrical wall means, said floor and wall means being constructed of at least one layer of horizontally adjacent insulating fire bricks, said wall means being provided with a plurality of peep holes vertically spaced from one another, each of said peep holes having a relatively small outer viewing opening diverging toward the interior of the furnace chamber;

an outer steel shell having an enclosed bottom and spaced fromthe outer surfaces of said firebricks,

said shell including defining a plurality of manual gripping handle means for manually lifting and transporting said kiln,

a kiln floor of insulation material substantially filling the bottom of the steel shell for supporting said furnace chamber,

a burner port forming an opening from said furnace chamber and extending through the side of said steel shell,

manually removable lid means, including handle means, for affording insertion and removal of objects to be fired and having a flue positioned centrally therein,

gas burner means secured to the outer side periphery of said kiln shell and in communication with said furnace chamber through said burner port for heating said furnace chamber, said gas burner means including a nozzle directed toward and spaced outwardly from said burner port;

insulating cover means being pivotally secured to the side of said steel shell for selective rotation into sealing engagement over the burner port;

a vent sealing plug, including manual gripping handle means, selectively positionable within said flue opening; said cover means and said plug cooperating to control the rate of the cooling of the fired chamber,

refractory castable means filling the space between said outer steel shell and all of said firebricks and extending to said kiln floor; said refractory castable means adhering to the outer surfaces of said firebricks and said steel shell for securing said firebricks in place,

said refractory castable means comprising an upper layer and a lower layer of refractory castable substances having different thermal expansion characteristics;

said bricks being freestanding relative to one another and being bonded solely at their outer surfaces, said bonding being accomplished by said refractory castable means;

said bricks, said refractory castable means, and said steel shell having respective heat expansion characteristics substantially inversely proportional to expected temperature gradient conditions such that said bricks, said refractory castable means, and said steel shell expand and contract in a substantially uniform manner.

7. A method of constructing a portable gas fired pottery kiln comprising the steps of:

forming a substantially cylindrical steel outer kiln shell having a sealed bottom and manual gripping handle means, positioning a kiln floor of block insulation material on the sealed bottom of the shell,

forming a substantially cylindrical furnace chamber of smaller diameter than said steel shell within said shell and being supported on said insulation material, such that said chamber includes a bottom surface of insulating fire brick and side walls of freestanding, horizontally adjacent, and inwardly tapered fire brick,

pouring an insulating refractory castable into the space formed between the furnace chamber walls and the steel shell thereby forming a monolithic structure; and

said steps of forming a shell, forming a chamber,

and pouring a castable include the steps of selecting firebrick, refractory castable, and steel shell materials having heat expansion characteristics substantially inversely proportional to expected temperature gradient conditions such that said firebrick, said refractory castable, and said steel shell expand and contract in a substantially uniform manner. 

1. A manually portable gas fired art pottery kiln comprising: an inner surface chamber defined by a furnace floor and upwardly extending wall means, said chamber being constructed of at least one layer of horizontally adjacent insulating firebricks, an outer steel shell having an enclosed bottom and spaced from the outer surfaces of said firebricks, said shell including means defining a plurality of manual gripping handle means for manually lifting and transporting said kiln, a kiln floor of insulation material substantially filling the bottom of the steel shell for supporting said furnace chamber. a burner port forming an opening from said furnace chamber and extending through said steel shell, gas burner means secured to the outer periphery of said kiln shell and in communication with said furnace chamber through said burner port for heating said furnace chamber, manually removable lid means, including handle means, for affording insertion and removal of objects to be fired and and having a flue positioned centrally therein, refractory castable means filling the space between said outer steel shell and all of said fire bricks and extending to said kiln floor; said refractory castable means adhering to the outer surfaces of said fire bricks and said steel shell for securing said fire bricks in place, said bricks being freestanding relative to one another and being bonded solely at their outer surfaces said bonding being accomplished by said refractory castable means. said bricks, said refractory castable means, and said steel shell having respective heat expansion characteristics substantially inversely proportional to expected temperature gradient conditions such that said bricks, said refractory castable means, and said steel shell expand and contract in a substantially uniform manner.
 2. The kiln according to claim 1 wherein said gas burner means includes a nozzle directed toward and spaced outwardly from said burner port; insulating port cover means being pivotally secured to said steel shell for selective rotation into sealing engagement over the burner port; and a vent sealing plug, including manual gripping handle means, selectively positionable within said flue opening; said cover means and said plug cooperating to control the rate of the cooling of the fired chamber.
 3. The kiln according to claim 2 wherein said burner port, said gas burner means, and said port cover are disposed at the side of said kiln.
 4. The kiln according to claim 1 wherein said refractory castable means comprises an upper layer and a lower layer of refractory castable substances having different thermal expansion characteristics.
 5. The kiln according to claim 1 wherein said cylindrical kiln wall means is provided with a plurality of peep holes vertically spaced from one another, each of said peep holes having a relatively small viewing opening diverging toward the interior of the furnace chamber.
 6. A manually portable gas fired art pottery kiln comprising: a cylindrical inner surface chamber defined by a furnace floor and upwardly extending cylindrical wall means, said floor and wall means being constructed of at least one layer of horizontally adjacent insulating fire bricks, said wall means being provided with a plurality of peep holes vertically spaced from one another, each of said peep holes having a relatively small outer viewing opening diverging toward the interior of the furnace chamber; an outer steel shell having an enclosed bottom and spaced from the outer surfaces of said firebricks, said shell including defining a plurality of manual gripping handle means for manually lifting and transporting said kiln, a kiln floor of insulation material substantially filling the bottom of the steel shell for supporting said furnace chamber, a burner port forming an opening from said furnace chamber and extending through the side of said steel shell, manually removable lid means, including handle means, for affording insertion and removal of objects to be fired and having a flue positioned centrally therein, gas burner means secured to the outer side periphery of said kiln shell and in communication with said furnace chamber through said burner port for heating said furnace chamber, said gas burner means including a nozzle directed toward and spaced outwardly from said burner port; insulating cover means being pivotally secured to the side of said steel shell for selective rotation into sealing engagement over the burner port; a vent sealing plug, including manual gripping handle means, selectively positionable within said flue opening; said cover means and said plug cooperating to control the rate of the cooling of the fired chamber, refractory castable means filling the space between said outer steel shell and all of said firebricks and extending to said kiln floor; said refractory castable means adhering to the outer surfaces of said firebricks and said steel shell for securing said firebricks in place, said refractory castable means comprising an upper layer and a lower layer of refractory castable substances having different thermal expansion characteristics; said bricks being freestanding relative to one another and being bonded solely at their outer surfaces, said bonding being accomplished by said refractory castable means; said bricks, said refractory castable means, and said steel shell having respective heat expansion characteristics substantially inversely proportional to expected temperature gradient conditions such that said bricks, said refractory castable means, and said steel shell expand and contract in a substantially uniform manner.
 7. A method of constructing a portable gas fired pottery kiln comprising the steps of: forming a substantially cylindricAl steel outer kiln shell having a sealed bottom and manual gripping handle means, positioning a kiln floor of block insulation material on the sealed bottom of the shell, forming a substantially cylindrical furnace chamber of smaller diameter than said steel shell within said shell and being supported on said insulation material, such that said chamber includes a bottom surface of insulating fire brick and side walls of freestanding, horizontally adjacent, and inwardly tapered fire brick, pouring an insulating refractory castable into the space formed between the furnace chamber walls and the steel shell thereby forming a monolithic structure; and said steps of forming a shell, forming a chamber, and pouring a castable include the steps of selecting firebrick, refractory castable, and steel shell materials having heat expansion characteristics substantially inversely proportional to expected temperature gradient conditions such that said firebrick, said refractory castable, and said steel shell expand and contract in a substantially uniform manner. 